Well dvd-r are cheaper to buy (cds) but the burners arnt. My dvd+rw was cheap ass from america and the disks are dearer than dvd-r's. and theres many differences on speeds while writing. You may want to read some reviews on your burner and see which disks you should use
dvd-r and dvd+r are just different formats. I know that dvd+r is a newer than dvd-r, so that's why some older players won't read those disks. Check the book on your buner, it will tell you which type of discs it can read/write.